IRSN, Institut de radioprotection et de sûreté nucléaire

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Research units

Radioelement Transfer Research Laboratory (LETR)


The Radioelement Transfer Research Laboratory (LETR) is located at the research centre of Cadarache, in South-East of France and headed by Jean Denis.


Note: Corium represents all the material resulting from the melting of the components of a nuclear reactor core. It is derived from the English word "core" to which has been added the Greek suffix “ium” standing for "element".





Context and research themes


The general objectives of the LETR are to improve, on the one hand, the understanding of the radioactive products behaviour and their associated phenomena, in the reactor vessel, its circuits and the containment, and, on the other hand, the understanding of the phenomena likely to cause damage to the containment (especially phenomena involving the corium outside the reactor vessel). This research work is aimed at better evaluating the radiological consequences in the event of a severe accident occurring in a nuclear pressurised water reactor. This research is subdivided into various subjects: the behaviour of fission products (FP) within nuclear fuels and their release from the fuel rods, their behaviour during transport in the circuits (deposition, chemical interactions), their behaviour in the containment, with special attention to the behaviour of iodine, and finally the behaviour of the corium outside the reactor vessel (interaction between corium and concrete).


The laboratory’s main activity is the production, improvement and validation of physical and chemical models on the basis of the experimental results  interpretation. These results are obtained mostly from IRSN's research programmes and programmes conducted in collaboration with international partners, such as those belonging to the Sarnet, the European Severe Accident Research NETwork of excellence. In this respect, LETR plays an important role in the specification and interpretation of experimental programmes.


LETR is responsible for incorporating these models into mathematical software (software development) and for validating them. It also develops databases on the thermodynamic and physical properties of nuclear materials. Finally, it participates in studies conducted with mathematical software, to support safety assessments.


The laboratory has a thorough knowledge of the following fields:

  • The physico-chemistry of fission products.
  • The physics of aerosols (transport, agglomeration, deposition).
  • Radiochemistry, particularly that of iodine in aqueous and gaseous phases.
  • Thermo-hydraulics and mass and energy transfers, particularly involving multi-components, multi-phase and chemically reactive materials.
  • Thermodynamics (modelling, phase diagrams, Calphad approach).
  • Scientific mathematical software development.


The laboratory is also very actively involved in many international networks working on improving the knowledge in the field of nuclear safety.



Specialties and researchers


Marc Barrachin, deputy head of laboratory, engineer
Loïc Bosland, engineer

Karine Chevalier-Jabet, engineer
Frédéric Cousin, engineer

Jean Denis, head of laboratory
Katia Dieschbourg, engineer
Roland Dubourg, engineer

Roland Ducher, engineer

Alexandre Figueiredo, PhD student (2017-2020)

Kasi Gajavalli, PhD student (2015-2018)

Tim Haste, engineer

François Kremer, engineer

Catherine Marchetto, engineer
Bénédicte Michel, engineer

Bruno Piar, engineer

Sidi Souvi, engineer

François Virot, engineer



Facilities and techniques


LETR has the following resources:

  • Scientific computational tools developed internally in the laboratory (Astec severe accident software) and mastering of external tools (thermochemistry programs GEMINI, Facsimile) in the field of FP physico-chemistry, in particular the iodine radiochemistry in aqueous and gaseous phases, and in the field of aerosol physics, thermalhydraulics, and mass and energy transfers.


  • Databases in the above mentioned topics :
  1. Literature documents
  2. Experimental data
  • Databases on the properties of nuclear materials (fission products and various constituents) especially at high temperatures: 
  1. physical properties
  2. thermodynamic and thermochemical properties

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Radioelement Transfer Research Laboratory
Bat. 702 - BP 3
13115 Saint-Paul-Lez-Durance
By phone: +33 (0)4 42 19 97 14


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